The present invention relates to a combined hemodialysis and hemofiltration (hemodiafiltration) process and apparatus and more particularly to a hemodiafiltration process and apparatus capable of causing dialyzate to migrate from a dialyzate side to a body fluid side of a membrane, and then causing an aqueous component or water to migrate from the body fluid side to the dialyzate side of the membrane in a dialyzer, repeatedly, for performing both dialysis and filtration to purify blood or other body fluid. The process and apparatus enable a highly efficient and easily executable purifying operation by means of making the process double purpose for hemofiltration (HF) and hemodialysis (HD). The present hemodiafiltration process and apparatus eliminate the replacement fluid introducing equipment which has been indispensable in conventional hemofiltration (HF) systems.
In recent years artificial kidneys, systems for purifying body fluid, such as blood or its ingredients, with the object of treating or maintaining the life of a patient suffering from renal insufficiency, have been widely employed. Such artificial kidneys include so-called dialyzers, which comprise semipermeable membranes, such as cuprammonium rayon membranes, in a casing, such membranes being of the film type, tube type, or hollow fiber type. The dialyzer of this type functions in the HD operation such that the body fluid, such as blood, is contacted with the dialyzate, the semipermeable membranes disposed therebetween for dialyzing and removing urea, uric acid, etc., accumulated in the body fluid of a patient (subject) so as to make the body fluid of almost normal solute concentration so as to be returned into the body of the patient. In the known HF operation, on the other hand, solution containing chiefly needless substances of middle and small molecular weight is removed from the blood by the filtering action of semipermeable membranes and solution containing indispensable substances is added to the blood to be returned to the body of the patient.
It is badly needed to have a system capable of executing both functions concurrently, so as to permit the removing capability of both HD and HF. No such a double purpose handy system capable of fulfilling both functions of HF and HD, in a single system, satisfactorily in high efficiency, has been developed yet. Another problem conventionally seen in the HF operation is the requirement for a replacement fluid introducing apparatus which infuses the replacement fluid containing the essential substances into the body and a regulating system for regulating at least one of the introducing speed of the replacement fluid and the filtering speed of the solution containing the needless substances from the side of the blood. Furthermore, the reducing amount and speed of the body fluid during the HF operation must be so controlled as to be agreeable with the predetermined schedule. A system attempting to satisfy such requirements inevitably becomes complicated in structure, highly precise, and consequently not simple in its operation mode. The disadvantages of the prior art are not confined to the above; other disadvantages include the necessity of the infusion fluid itself for the replacement of body fluid, and the problem of its transportation and storage. Due to all of the circumstances which have made the HF operation expensive and complex, development of a new hemodiafiltration system which is inexpensive in manufacturing cost and highly efficient in dialysis and filtration is badly needed.